Well I don't think so, "the best or not the best", that depends on who his opponent is and how his opponent fights.
According to The Law of Conservation and Transformation of Energy, the total amount of energy in an isolated system remains constant, although it may change forms.
Therefore Yang Guo's total amout of energy in sad mode = that in normal mode.
In sad mode, YG's energy utilization is increased.
But the total amout of energy still stays the same, thus, the endurance of the Sad Mode Yang Guo < that of the Normal Mode Yang Guo.
I drew a graph to represent this matter. lolz I used the Paint application of Windows so it's very ugly, hope you'll understand what I mean
:
$this->handle_bbcode_img_match('http://img95.imageshack.us/img95/5444/graphhm9.png')
As you can see from the graph, YG's palm energy is boosted up only throughout the t1t2 period, so if the opponent is cautious about Yang Guo from t1 and keeps dragging the fight on to t2, then from t2 on, he/she will gradually gain the upper hand over Yang Guo.
, and when the time reaches t3, YG's power will be exhausted and that will result in him being killed by the opponent.